3.091 OCW Scholar
Self-Assessment Exam
Aqueous Solutions
Solution Key
2009 Exam 3, Problem #3
(a) Calcium ammonium phosphate (CaNH4PO4) dissolves in water according to
–
CaNH4PO4(s) ∏ Ca2+(aq) + NH4+(aq) + PO43 (aq)
–
for which the value of the solubility product, Ksp, has been determined to be 4.4 × 10 14. Calculate
the solubility of CaNH4PO4 in water. Express your answer in units of molarity, i.e., moles of
CaNH4PO4 per L of solution.
(b) Calculate the solubility of CaNH4PO4 in 2.2 M CaBr2(aq). Express your answer in units of molarity.
–
Assume that in water CaBr2 completely dissociates into Ca2+ cations and Br anions.
Final Exam, Problem #10
(a) You have 333 mL of alkaline solution at pH = 9.9. You wish to neutralize this by reacting it with
222 mL of acid. What must be the value of the pH of the acid?
(b) Name the conjugate base of each of the following:
2
(1) HPO42–
(2) CH3NH3+
(c) Classify each of the following as a Lewis acid or a Lewis base:
2
(1) CN
–
(2) H2O
(d) Consider the effect each of the following substances has on the ionization of the weak base, ammonia
(NH3(aq)). For each, state whether the substance (1) suppresses ionization, (2) enhances ionization,
or (3) has no effect on the ionization of ammonia. In each instance, give a reason for your choice.
6
(i) KOH
(ii) HCl
(iii) NH4Cl
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3.091SC Introduction to Solid State Chemistry
Fall 2009
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